The present application claims priority under 35 U.S.C. xc2xa7119 of German Patent Application No. 197 54 807.5, filed on Dec. 10, 1997, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention is related to a process for production of fittings for mechanical processing of suspended fibrous material. The fittings include at least one base and at least one processing element adapted to be exposed to flow of the fiber suspension during operation of the fitting.
2. Discussion of the Background Information
Fittings produced in the manner generally discussed above are used for mechanical processing of suspended fibrous material, e.g., beating of paper pulp, dispersion of contaminants and fibers as well as deflaking, i.e., breaking down of fiber agglomerations. Fittings are, e.g., built into beaters or xe2x80x9crefiners.xe2x80x9d The suspension in refiners has a solid content of approximately 2-8% wt. Similar pulp densities are also established in deflakers. Impellers used in pulpers may also have fittings similar in general to those discussed above, in which wet crushing of an introduced fibrous material is performed. Machines for higher pulp densities, e.g., high-consistency mills, dispersers, or kneaders, are utilized for mechanical processing the entire fibrous material, i.e., to disperse foreign matter contained therein. Such machines have at least one rotor and at least one stator with either disk-shaped or cone-shaped surfaces onto which the fittings are applied so that gaps may be formed between them. Many fittings have webs and grooves on their work surfaces, sometimes referred to as xe2x80x9cknife fittings.xe2x80x9d Other fittings have the shape of toothed rings. Moreover, it is known that, in addition to the shape of the webs, grooves, and teeth, the material from which these fittings are made also affects the processing of the fibrous material.
The fittings are exposed to wear and, consequently, must be replaced at specific intervals. However, during their service life, wear may cause the processing action to change because the shape and surface of the fittings have a great influence on the processing effect.
Thus, it is understandable that a significant expense, which is reflected in the specific design of shape and choice of the materials, is incurred in developing fittings. It has been demonstrated that materials which are particularly suited for use as processing elements have properties which may be very problematic for use as a base of the fitting. This is particularly true of materials which are very hard and brittle, e.g., ceramics, and, consequently, which do not have the necessary ductility for the base. Furthermore, such materials are relatively expensive, time-consuming to produce, and can be used only at great expense compared to standard metal materials.
The base of a processing tool provides a connection of the processing element to the remaining components, e.g., the components of a beater. Due to the high forces which occur in such beaters, particularly high strength requirements are required for the base. It must also be possible to reliably attach the base to the beater, in particular, via high-stress screws. Because of these requirements, a particularly strong and ductile material is essential for the producing the base.
A process for production of fittings is known from DE 196 03 548 A1, in which the fittings are assembled from separately manufactured parts. However, this publication only very generally discusses a bonding means that is applied between the base and processing element, but specifically identifies the very expensive high-temperature vacuum welding process or gluing processes. However, these processes cannot always be used, i.e., they are too expensive for many applications, and, when used in the more inexpensive processes, yield strengths which are not always adequate.
The present invention provides a process for the production of fittings in which particularly well-suited brittle materials may be used as processing elements and may be bonded relatively simply to the base.
In this regard, the process of the present invention includes producing an elastic bond between the processing elements and the base.
Thus, the present invention, as with the known production processes discussed above, may utilize different materials for the processing elements and for the base. As discussed above, this may be of significant advantage in that the selection of material for the processing element is based on a desired processing technology, whereas selection of the material for the base is primarily based on its strength and is optimized in terms of cost.
According to the features of the present invention, the connection between bases and processing elements is elastic, sufficiently precise, and, overall, cost-effective. Thus, because the parts connected together are not intended to move relative to each other, a damping action due to the elastic layer provides favorable performance. For example, the elastic layer may attenuate stress peaks and also reduce the often troublesome noise generation of these type machines. Vulcanization is a process already widespread in production engineering which has proven itself even under demanding conditions in, e.g., the chassis of motor vehicles, where it is used for the connection of steel parts which move against each other. Surprisingly, with the coupling of ceramic and steel, vulcanization provides the necessary properties for the applications to be performed by the fittings. The same is true for bonds made with elastic layers such as, e.g., silicone or elastic plastics. Thus, a homogeneous layer that adheres on both sides and cures such that it remains largely elastic may be formed, or a finished layer of elastic material may be glued on both sides.
The formation of an intermediate layer having a thickness of, e.g., between approximately 0.5-2 mm, may also compensate for any differing expansion characteristics of the joined parts. As is known, the coefficients of thermal expansion of ceramic and steel differ significantly, which causes problems with rigid connections.
It may also be beneficial that the temperatures during vulcanization or gluing may be far below the melting points of the parts joined.
Moreover, the present invention facilitates re-machining worn fittings by removing the remains of the old processing element and replacing it with a new one.
The present invention is directed to a process for production of fittings for a mechanical processing of suspended fibrous material that include at least one base and at least one processing element adapted to be exposed to flow of a fibrous suspension during operation. The process includes separately producing the at least one base and the at least one processing element, placing an elastic bonding material between contact surfaces of the at least one base and the at least one processing element, and elastically bonding the at least one base and the at least one processing element without melting the processing elements.
In accordance with another feature of the present invention, after the elastic bonding, an elastic layer having a thickness of at least approximately 0.5 mm may be formed between the at least one base and the at least one processing element. Further, after the elastic bonding, the elastic layer formed between the at least one base and the at least one processing element has a thickness of at least approximately 1.0 mm.
In accordance with another feature of the present invention, the elastic bonding may include vulcanizing the elastic bonding material. The elastic bonding material may be composed of a polymer. Further, the vulcanizing may include setting a temperature at the contact surfaces between approximately 100xc2x0 C. to 150xc2x0 C. The vulcanizing may include maintaining an absolute pressure of under at least approximately 3 bar. The vulcanizing may include providing an air/steam atmosphere. The polymer may be composed of a synthetic rubber.
In accordance with still another feature of the present invention, the placing of the elastic bonding material may include forming the polymer into a sheet, attaching the polymer sheet to the at least one base, and placing the at least one processing element on the polymer sheet.
In accordance with a further feature of the present invention, the elastic bonding material may form an elastic layer after the elastic bonding, and the process further includes gluing the elastic layer to the at least one base and to the at least one processing element. Further, the elastic bonding material may be composed primarily of silicone. The elastic bonding material may be composed of a plastic sheet that is coated on both sides with an adhesive.
In accordance with still another feature of the present invention, the at least one processing element may be composed at least partially of ceramic.
In accordance with a still further feature of the present invention, the at least one processing element may be composed of a ceramic composite material.
In accordance with another feature of the present invention, the at least one processing element may include ridges located on a side adapted to be positioned toward the pulp suspension. The ridges may extend above a base of a groove by between approximately 2 and 20 mm.
In accordance with still another feature of the present invention, the at least one processing element may include a substantially porous surface.
In accordance with a further feature of the present invention, the at least one base may include at least one recess. The at least one processing element may include at least one projection, and the process may further include inserting the at least one projection into the at least one recess prior to the elastic bonding. After inserting the at least one projection into the at least one recess, a gap remains in the recess. The remaining gap may have a thickness that corresponds to a thickness of the elastic bonding material. The elastic bonding material may be inserted into the remaining gap prior to elastic bonding.
In accordance with a further feature of the present invention, the process may further include applying the elastic bonding material to a continuous surface of the at least one base, positioning the at least one processing element on the elastic bonding material, and holding the at least one processing element with a holding device during the elastic bonding.
In accordance with another feature of the present invention, the process may further include forming the elastic bonding material as a strip of material with projections extending substantially perpendicular on at least one side, placing the projections into corresponding openings in one of the at least one processing element and the base, and bonding the projections to the contact surfaces of the openings via vulcanization. The projections may extend substantially perpendicular to both sides of the strip material. The projections extending substantially perpendicular to the strip material may have thickened portions that, while placing the projections into the one of the at least one processing element and the base, may be elastically compressed and, after joining, may expand into the openings to fix the parts in the elastic bonding.
In accordance with still another feature of the present invention, before vulcanization, the process may include inserting knobs composed of a polymer through holes that penetrate one of the processing element and the base, and connecting the knobs to the layer by vulcanization.
In accordance with a still further feature of the present invention, the base may be composed of a steel alloy having a strength of at least about 300 N/mm2.
In accordance with a still further feature of the present invention, the base may be shaped as a torus.
In accordance with another feature of the present invention, the base may be substantially shaped as a segment of a torus.
In accordance with another feature of the present invention, the base may be shaped as a truncated cone.
In accordance with a further feature of the present invention, the process may further include coupling the base and processing elements with a screw connection.
In accordance with still another feature of the present invention, the process may further include coupling the base and processing elements with a groove and projection connection.
The present invention may also be directed to a fitting for processing suspended fibrous material. The fitting includes a base adapted for attachment to a processing machine, at least one processing element adapted to be exposed to a stream of a fibrous material suspension during operation of the fitting, and an elastic layer located between the base and at least one processing element to couple the at least one processing element to the base.
In accordance with another feature of the present invention, the at least one processing element may be adapted for movement relative to another processing element to process the suspended fibrous material.
In accordance with still another feature of the present invention, the elastic layer may be composed of a vulcanized polymer.
In accordance with a further feature of the present invention, the elastic layer may have a thickness of least approximately 0.5 mm.
In accordance with a still further feature of the present invention, the elastic layer may have a thickness of least approximately 1.0 mm.
In accordance with yet another feature of the present invention, the at least one processing element and the base may be made of different materials.
The present invention may also be directed to a machine for mechanical processing of suspended fibrous material. The machine includes at least two fittings mounted for relative movement to each other. At least one of the at least two fittings may include at least one base that is at least one of rotatably and non-rotatably mounted, at least one processing element adapted to be exposed to the suspended fibrous material, and an elastic layer located between the base and at least one processing element to couple the at least one processing element to the base.
The present invention may also be directed to a process for producing a processing machine for mechanically processing suspended fibrous material in a machine including at least two fittings, at least one of the at least two fittings including at least one base, at least one processing element. The process includes forming at least one of the at least two fittings by separately producing the at least one base and the at least one processing element, placing an elastic bonding material between contact surfaces of the at least one base and the at least one processing element, and elastically bonding the at least one base and the at least one processing element without melting the processing elements mounted for relative movement to each other. The process may also include mounting the at least two fittings for movement relative to each other.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.